#include <iostream>
#include <algorithm>

using namespace std;

const int N = 510,INF = 1e9;
int n;
int a[N][N];
int f[N][N];


int main()
{
	scanf("%d",&n);
	for(int i = 1; i <= n;i++)
		for(int j = 1;j<=i;j++)
			scanf("%d",&a[i][j]);
	for(int i = 0;i <= n ;i ++)
		for(int j = 0; j <= i+1 ; j ++)
			f[i][j] = -INF;
	f[1][1] = a[1][1];
	for(int i = 2;i <= n; i ++)
		for(int j = 1;j <= i; j++)
			f[i][j] = max(f[i-1][j-1]+a[i][j], f[i-1][j] + a[i][j]);
	
	int res = -INF;
	for(int i = 1;i<n;i++) res = max(res,f[n][i]);
	printf("%d",res);
	
	return 0;
 } 
